Stator blade positioning means



I I t a July 17, 1956 N. c. SIMONSEN 2,755,064

STATOR BLADE POSITIONING MEANS Filed Aug. 50, 1950 A20 //4 )f illi I 'I I I n I I,

IIIII INVEN TOR. NELEIUN C. EIMEINSEN.

. BYZVZ;

ATTORNEY United States Patent i STATOR BLADE POSITIONING MEANS Nelson C. Simonsen, Clifton, N. J., assignor to Curtiss- Wright Corporation, a corporation of Delaware Application August 30, 1950, Serial No. 182,331

6 Claims. (Cl. 253-78) This invention relates to fluid mechanisms such as fluid compressors, turbines or the like, and is particularly directed to means for positioning the stator blades of such mechanisms. The invention is herein illustrated and de scribed in connection with an axial flow compressor but, as will become evident, the invention is not limited to this specific application.

Axial flow compressors, such as used in gas turbine engines, generally have a large number of stages of stator blades with each stage comprising a large number of close circumferentially spaced stator blades. In addition, in order to reduce the weight of the compressor, as is highly desirable in case of a gas turbine power plant, for aircraft, the compressor housing for such a power plant may have light-weight thin-wall construction. With such a thin-wall housing construction the provision of a simple structure for securing the large number of closely spaced stator blades in their proper positions to a wall of said housing has presented a difiicult problem. For example, in the past stator blades have been welded to their housing. This obviously is a laborious procedure particularly, because the orientation of each blade must be accurately controlled. In accordance with another prior construction the shank of each stator blade has a stem projecting through a wall of the stator housing and the end of each stem is provided with a flat which is used to properly orient the blade, each blade being separately adjusted to its proper position. Thus assembly of the stator blades is also quite laborious with this latter construction.

An object of this invention comprises the prevention of a novel, simple, and effective construction for securing the stator blades to their housing wall such that said blades automatically assume their proper positions about their respective longitudinal axes.

In accordance with the present invention each stator blade has a portion with a spherical surface which is drawn up tight against a corresponding spherical surface at the bottom of an annular groove in the stator housing when the blade is secured to said housing and said portion has a non-circular periphery fitted within a non-circular hole in a ring co-axially disposed in said groove whereby said non-circular hole determines the orientation of said blade about its longitudinal axis and locks the blade in this position.

Other objects of the invention will become apparent upon reading the annexed detailed description in connection with the drawing in which:

Figure l is a schematic view of a portion of an axial flow compressor;

Figure 2 is an enlarged sectional view of a portion of a compressor housing illustrating the structure of the present invention for securing stator blades to said housing.

Figure 2A is a view similar to Figure 2 but illustrating a modified construction;

Figure 3 is a sectional view of only the compressor housing taken along line 33 of Figure 2;

Figure 4 is a fragmentary view of a portion of the blade positioning ring incorporated in Figure 2 or 2A;

Figure 5 is a sectional view taken along line 5'5 of Figure 4;

7 modified ring;

Figure 7 is a side view of a stator blade; and

Figure 8 is a view taken along line 88 of Figure 7.

Referring first to Figure l of the drawing, an axial flow fluid compressor 10 is schematically illustrated as comprising a rotor 12 mounted for rotation within a housing 14, the annular space between said rotor and housing comprising the fluid flow path through which fluid is drawn from the compressor inlet 16 and discharged in a compressed condition at the other end of said path. A plurality of axially-spaced stages of blades 18 are carried by and project radially outwardly from the rotor 12 and a plurality of axially spaced blades 26 are carried by and project radially inwardly from the inner cylindrical wall 22 of the stator housing 14, the stages of stator blades 2!) alternating with the stages of rotor blades 18 as illustrated. The axial flow compressor construction so far described is conventional and as is well known such compressors are commonly used for example, in gas turbine engines for supplying the turbine combustion chamber with compressed air.

Referring now particularly to Figures 2 to'8 of the drawing, the housing wall 22 has a cylindrical inner surface 24 in which are machined or otherwise formed a plurality of axially-spaced annular grooves 26, each of said grooves being coaxial with the axis 25 of the compressor rotor, there being one such groove for each stage of stator blades. Figure 2A illustrates a modification in which the annular grooves 26 are replaced by annular grooves 26a of modified construction. In any one compressor housing however, said grooves would preferably all be of the same construction.

A plurality of sets of holes 28 are formed in the housing wall 22, there being one set of holes 23 for each groove 26 or 26a, with the holes of each groove being circumferentially spaced and disposed in a plane substantially midway between the axially spaced side shoulders of its groove. The bottom surface 36 of each groove 26 is made spherical from one side shoulder to the other with the center 32 of said spherical bottom surface being disposed in the plane of its associated holes 28 and with said surface having a radius of curvature A such that said center 32 is on the axis 25 of the compressor rotor. Ring means 36, preferably of sheet metal, is received within each groove 26 between the side shoulders 35 of said grooves. For reasons of assembly, each ring means 36 may, for example, comprise of onepiece split construction or it may be made in a plurality of sections disposed in end-to-end relation. Said ring means is suitably secured to the housing wall 22, for example, by peening the adjacent housing wall over the axially-spaced side edges of the ring means at circumferentially spaced points therealong as indicated at 34.

If as illustrated in Figure 2, the entire bottom surface of the groove 26 is spherical, then only the two edges of the ring means -36 will seat against said bottom surface. If a larger seating area for the ring means is desired, the bottom groove surface may be modified to that of the groove 26a (Figure 2A) wherein each edge of the groove bottom surface is machined to a cylindrical surface as indicated at 37. The grooves 26 and 26a are otherwise identical.

It should be noted that with an identical radius A for the bottom surface 3% of the grooves 26 and 26a and with said grooves being of the same width, a ring means 36 of slightly greater thickness is required for the groove 26:; in order that said ring means be flush with the stator wall surface 24. In Figure 2A no ring means 36 has been illustrated in the groove 26a in order to permit illustration of the surfaces 37.

A plurality of circumferentially spaced openings 38 are punched through or otherwise formed in each ring means 36, there being one opening 38 for each wall hole 28. Each opening 38 has a non-circular periphery which is substantially larger than the periphery of the Wall holes 28 so that with each said opening 38 registering with a hole 28, each said opening 38 uncovers a portion of the groove bottom spherical surface 30 surrounding said hole. As illustrated, the periphery of each opening 38 comprises a pair of straight sides 39 of equal length and disposed parallel to the axially spaced edges of the ring means 36, said straight sides being interconnected by a pair of concentric circular sides 41.

Each stator blade 20 (only one of which is illustrated in Figure 2) has an airfoil or fluid working portion which projects radially inwardly into the annular fluid space between the stator wall 22 and the compressor rotor 12. The shank or root end of each stator blade comprises a stem portion 40 and a shelf or annular flange portion 42 which projects laterally from the shank stem adjacent to the blade airfoil portion to form the butt end of the blade. The shank end side of the annular blade shelf or flange 42 is formed with a spherical surface having the same radius A as the radius of the groove spherical bottom surface 30 with the center of said blade spherical surface being disposed on the axis of the blade shank stem 40. In addition the periphery of the shank shelf or flange 42 of each blade is identical to that of the openings 38.

With the threaded stem 40 of a stator blade 20 inserted through a hole 28 in the stator wall 22 and with the shelf or flange 42 of said blade fitted within the associated opening 38 in the ring means 36, said blade may be secured to the stator wall 22 by threading a nut 44 on the outwardly projecting end of the stator blade stem 40 whereby, when said nut is tightened, the spherical surface of the blade shelf or flange 42 is drawn against the groove bottom spherical surface 30. The mating spherical surfaces of the blade shelf and the bottom of the groove permit the blade shelf 42 to seat against the bottom of said groove regardless of the orientation of the blade about the axis of its stem 40. Furthermore, because the peripheries of each blade shelf 42 and its mating opening 38 in the ring means 34 are identical and are non-circular, said openings 38 determine and fix the position or orientation of the blades 20 about their longitudinal axes and each blade is thereby positively locked in this position against angular displacement about its longitudinal axis. Thus as each stator blade is inserted into position on the stator housing wall 22 the blade working or airfoil portion automatically is properly positioned about the axis of its stem 40 as a result of the mating engagement of its blade shelf 42 with the associated hole 38 whereby assembly of the stator blades on the stator wall 22 is relatively simple.

Since the non-circular openings 38 in the ring means 36 automatically fix the orientation of the stator blades, said blade orientation may set as desired by properly orienting said openings in said ring means. For example, Figure 6 illustrates a ring means 361! in which the openings 38a have the same peripheral shape as the openings 38 but the straight side walls of the openings 38:! are inclined slightly, as illustrated, to the side edges of the ring means 36:: instead of being parallel thereto as in the ring means 36. The ring means 36 and 36a are otherwise identical so that if the ring means 36a were used in place of the ring means 36 the orientation of the stator blades about their longitudinal axes would be changed by an angle equal to the difference between the angles made by the straight sides of the holes 38 and 38a relative to the planes of their respective ring means. In general the clearance between the shank end of the airfoil portion of each blade 20 and the stator wall 22 is quite small so that the profile given to the shank end of each blade airfoil portion depends on the orientation or position the blade airfoil is to have. Thus substantially the same stator blade could be used with either the ring means 36 or 36a.

From what has been said it should be apparent that the openings 38 in the ring means 36 need not have .the specific non-circular shape illustrated. Thus as long as the mating peripheries of each blade shelf 42 and its associated opening 38 are non-circular, the orientation of the stator blades 30 about their longitudinal axes will i is such that when seated against the bottom of its groove,

said shelf lies flush with the adjacent surface of its said ring means. Therefore the wall surface 24, the ring means 36 or 36a and the blade shelves 42 together provide a smooth and continuous boundary for the compressor fluid flow path from which the airfoil portions of the stator blades project.

The aforedescribed construction of the present invention not only simplifies assembly of the stator blades by automatically properly positioning said blades, but the construction itself is simple to fabricate in that all the machining operations on the stator housing can be performed by machines all of which are generally found in a machine shop. Thus the annular grooves 26 are turned in a vertical turret lathe, the stator housing holes 28 are drilled in a horizontal boring mill and the openings 38 in the ring means are formed with a punch press.

While I have described my invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modifications.

I claim as my invention:

1. In combination; a rotary axial flow mechanism, such as a compressor, turbine or the like, having a non-rotating annular wall co-axial with the axis of rotation of said mechanism, said wall forming a boundary for the fluid flow path of said mechanism and having a co-axial annular groove therein with the bottom of said groove being a spherical surface having the center, about which said spherical surface is described, disposed on said axis; ring means co-axially disposed in said groove with said ring means being substantially flush with the adjacent surface of said wall; and a plurality of circumferentiallyspaced blades secured to said wall and having a working portion projecting from said wall into said flow path and having a shank portion extending through an opening in said ring means with said shank portion having a spherical surface of substantially the same curvature as that of the bottom spherical surface of said groove and held against said groove bottom spherical surface; and cooperating surfaces on each said blade and said ring means for locking said blade against angular displacement about its longitudinal axis.

2. In combination; a rotary axial flow mechanism, such as a compressor, turbine or the like, having a non'rotating annular wall co-axial with the axis of rotation of said mechanism, said wall forming a boundary for the fluid flow path of said mechanism and having a co-axial annular groove therein with the bottom of said groove being a spherical surface having the center, about which said spherical surface is described, disposed on said axis; ring means co-axially disposed in said groove; and a plurality of circumferentially-spaced blades each having a shank comprising a stem with a laterally projecting flange disposed adjacent to the blade working portion and with the shank end side of said flange having a spherical surface of substantially the same curvature as said groove bottom spherical surface, said ring means and blade flanges forming a smooth continuation of the adjacent surface of said wall, each of said blades having its shank projecting through an opening in said ring means with said shank stem extending into said wall to secure said blade to said Wall with said flange spherical surface disposed in engagement with the spherical bottom surface of said groove; and cooperating surfaces on said blade shank flange and ring means for locking said blade against angular displacement about its longitudinal axis.

3. In combination; a rotary axial flow mechanism, such as a compressor, turbine or the like, having a non-rotating annular wall coaxial with the axis of rotation of said mechanism, said wall forming a boundary for the fluid flow path of said mechanism and having a co-axial annular groove therein with the bottom of said groove being a spherical surface having the center, about which said spherical surface is described, disposed on said axis; ring means co-axially disposed in said groove; and a plurality of circumferentially-spaced blades each having a shank comprising a stem with a laterally projecting flange disposed adjacent to the blade Working portion and with the shank end side of said flange having a spherical surface of substantially the same curvature as said groove bottom spherical surface, said ring means and blade flanges forming a smooth continuation of the adjacent surface of said wall, each of said blades having its shank projecting through an opening in said ring means with said shank stem extending into said wall to secure said blade to said wall and with said shank flange spherical surface disposed in engagement with the spherical bottom surface of said groove and with said shank flange disposed within said opening in said ring means, the shank flange of each blade and the ring opening in which said flange is disposed having mating non-circular peripheries for locking said blade against angular displacement about its longitudinal axis.

4. In combination; a rotary axial flow mechanism, such as a compressor, turbine or the like, having a non-rotary annular wall With a cylindrical inner surface co-axial with the axis of rotation of said mechanism and forming a boundary for the fluid flow path of said mechanism, said cylindrical surface having a co-axial annular groove therein with the bottom of said groove being a spherical surface having the center, about which said spherical surface is described, disposed on said axis; ring means coaxially disposed in said groove; a plurality of circumferentially-spaced blades each having a shank comprising a stem with a laterally projecting flange disposed adjacent to the blade working portion and with the shank end side of said flange having a spherical surface of substantially the same curvature as said groove bottom spherical surface, said ring means and blade flanges forming a smooth continuation of the adjacent surface of said wall, each of said blades having its shank projecting through an opening in said ring means with said shank stem extending into said wall and with said shank flange disposed within said opening in said ring means, said flange and opening having engaging surfaces locking said blade against angular displacement about its longitudinal axis; and means engaging said stem for detachably securing said blade to said wall with said shank flange spherical surface disposed against the spherical bottom surface of said groove.

5. In combination; a rotary axial flow fluid mechanism, such as a compressor, turbine or the like, having a nonrotating annular wall with a cylindrical inner surface coaxial with the axis of rotation of said mechanism and forming a boundary for the fluid flow path of said mechanism, said cylindrical surface having a co-axial annular groove therein with the bottom of said groove being a spherical surface having the center, about which said spherical surface is described, disposed on said axis and with said wall having a plurality of circumferentially spaced holes extending therethrough from the bottom of said groove; ring means co-axially disposed in said groove and having a plurality of circumferentially-spaced noncircular openings therethrough, there being one of said non-circular openings for each of said wall holes with each non-circular opening uncovering its associated wall hole and a portion of the adjacent spherical bottom surface of said groove; and a plurality of circumferentially spaced blades, one for each of said wall holes; each of said blades having a fluid working portion at one end projecting into said fluid flow path and a shank at its other end including stem and shelf portions with said shank stem portion projecting through one of said wall holes and with said shank shelf portion being received in the associated opening in said ring means, said shank shelf portion having a non-circular periphery similar to the periphery of its associated opening in the ring means to position said blade about its longitudinal axis and the shank end side of said shelf portion having a spherical surface of substantially the same curvature and engaging the adjacent spherical bottom surface of said groove said ring means and shelf portions forming a smooth continuation of the adjacent portions of said cylindrical wall surface; and means cooperating with the projecting shank stem portion of each blade for securing said blade to said wall with the spherical surface of the blade shelf pressed against the spherical bottom surface of said groove.

6. In combination; a rotary axial flow fluid mechanism, such as a compressor, turbine or the like, having a non-rotating annular Wall With a cylindrical inner surface co-axial with the axis of rotation of said mechanism and forming a boundary for the fluid flow path of said mechanism, said cylindrical surface having a co-axial annular groove therein with the bottom of said groove being a spherical surface having the center, about which said spherical surface is described, disposed on said axis and with said wall having a plurality of circumferentially-spaced holes extending therethrough from the bottom of said groove; ring means co-axially disposed in said groove and having a plurality of circumferentiallyspaced non-circular openings therethrough, there being one of said non-circular openings for each of said wall holes with each non-circular opening uncovering its associated wall hole and a portion of the adjacent spherical bottom surface of said groove; and a plurality of circumferentially-spaced blades, one for each of said wall holes; each of said blades having a fluid working portion at one end projecting into said fluid flow path and a shank at its other end, said shank including a stem projecting into one of said wall holes and a flange projecting laterally from said stem adjacent to its blade working portion and being received in the associated opening in said ring means, said shank flange having a non-circular periphery similar to the periphery of its associated opening in said ring means to position said blade about its longitudinal axis and the shank end side of said flange having a spherical surface of substantially the same curvature and engaging the adjacent spherical bottom surface of said groove, said ring means and the flanges of said blades being substantially flush with the adjacent portions of said cylindrical wall surface; and means cooperating with the projecting shank stem of each blade for detachably securing said blade to said wall with the spherical surface of the blade flange pressed against the spherical bottom surface of said groove. 7

References Cited in the file of this patent UNITED STATES PATENTS 841,503 Gelpke et al. Jan. 15, 1907 953,526 Green Mar. 29, 1910 1,997,506 Adamcikas et al. Apr. 9, 1935 2,412,365 Sollinger Dec. 10, 1946 FOREIGN PATENTS 478,104 Great Britain Jan. 12, I938 

